(i) Substances which can be decomposed by decomposers into useful products.
(ii) They do not cause poUution.
(iii) Example : Organic waste.
(i) They cannot be decomposed by the decomposers.
(ii) They cause huge poUution.
(iii) Example: Plastic.
(b) Acid rain is corroding the calcium carbonate of Taj Mahal and causing pits in the monument.
(c) It is a mixture of fog and smoke.